A screw conveyor for the transport of flowable substances and/or material as referred to initially may be used in connecting with meat-mincing machines, but it could also be used in other constructions, in which flowable substances are to be pumped by a positive displacement pumping function. Special problems arise, however, if the flow of substances has to be interrupted (periodically), for instance if the screw conveyor is used for carrying out filling operations in sausage manufacturing. In this application a clip device is coupled to the outlet from the screw conveyor so that the otherwise continues flow of substance through the outlet from the conveyor is periodically interrupted. This interruption may cause problems with overfilling of the pumping chamber in the conveyor and it has been known to solve this problem by stopping the conveyor during the clipping period.